Industrial gas compressors can be arranged in compression trains, which are used in a variety of industries to provide increased pressure in process fluids. Examples of such industrial uses include petroleum refineries, offshore oil production platforms, pipeline compressor stations, LNG liquefaction systems, and others. In many of these applications, space is at a premium and, thus, there is an ever-increasing demand for more compact compression systems. The development of “compact compressors” has enabled significant size reductions via combining a pressurized, high-speed motor and magnetic bearing system with the compressor in a single, hermetically-sealed motor-compressor module. One such system is the DATUM® C, which is commercially-available from Dresser-Rand Company of Olean, N.Y., USA.
These compact compression systems generally provide a higher motor power density and eliminate at least some of the gearboxes and traditional lubrication systems, thereby achieving significant reductions in size. However, these systems are typically packaged with conventional, external process equipment modules, including heat exchangers. Such heat exchangers are used either to limit the temperature of the process gas or to minimize the power required for gas compression. While proven reliable and suitable for a variety of different applications, the use of external heat exchangers often requires multiple compressor casing penetrations and significant interconnecting piping between the heat exchangers and the compressor. Accordingly, this scheme often results in a relatively large and complex compressor package.
Other compression system designs have attempted to integrate the heat exchangers within the compressor casing. While offering some improvement over traditional discrete component solutions, these designs generally increase the size of the compressor casing, both radially and axially, to provide the additional volume required to house the heat exchangers, thus somewhat defeating the size reduction/compact design intent of the system. Moreover, the number of compression stages that can be used is generally limited, as the size increase for additional heat exchangers compounds the size increase required for the additional stages. This generally results in a reduced pressure rise capability of the overall compression package. Further, the integration of such heat exchangers has, in some cases, led to significant losses in aerodynamic efficiency in the compressors.
What is needed is a compact compression system that provides integral process gas cooling, without suffering from the described drawbacks.